The Government has rights in this invention pursuant to Contract No. N66001-87-C-0205, awarded by the Department of the Navy.
The present invention relates generally to devices for coupling a collimated light beam into an optical waveguide and specifically into a rectangular raised channel waveguide formed on a substrate.
Various coupling methods for cylindrical optical devices are known. Coupling into optical fiber having cylindrical symmetry for single mode allows the alignment to an optical axis related to the circumference or physical shape of the optical fiber. Applicant's invention is directed to a different need. The need that applicant's invention addresses is the multimode coupling of a collimated free space beam to an optical waveguide that does not have cylindrical symmetry, but rather has rectangular symmetry.
An approach to this problem in the past has been to cleave or polish both the end of the waveguide structure and the media it is to couple to and then physically position o butt couple the waveguide to the media. Butt coupling has a high degree of sensitivity to transverse or lateral misalignment. In addition it requires labor intensive and therefore expensive machining of the waveguide endface or other optical element that is to be coupled.
Thus a need exists for a device which couples a collimated free space light beam to a rectangular raised channel waveguide on a surface and does not require machining of the surface or complicated alignment methods.